WO2013132612A1

WO2013132612A1 - Active sludge treatment method, and method for improving existing wastewater treatment facilities using said method

Info

Publication number: WO2013132612A1
Application number: PCT/JP2012/055812
Authority: WO
Inventors: 藤野　清治
Original assignee: 日本アルシー株式会社
Priority date: 2012-03-07
Filing date: 2012-03-07
Publication date: 2013-09-12
Also published as: JP5968420B2; US9446972B2; JPWO2013132612A1; US20150027947A1

Abstract

　The purpose of the present invention is to provide an active sludge treatment method generating almost zero excess sludge, and a method for improving existing drainage treatment facilities using the treatment method. The method comprises: a step (1) for supplying a sludge (2), generated by a settling tank, to a raw water aeration adjustment tank for wastewater which is to be subjected to active sludge treatment; a step (2) for adjusting the aeration of the raw water into which the sludge (2) has been mixed, such that the redox potential of the raw water is the correct value, and then supplying the raw water into a pressure flotation concentration and separation tank; a step (3) in which a sludge (1), generated by means of treatment in the pressure flotation concentration and separation tank, is supplied to a microbial reaction tank; a step (4) in which treated raw water (1), separated from the pressure flotation concentration and separation tank, is supplied to a dilute active sludge aeration tank and treated; a step (5) in which discharged water and a sludge (3) generated by means of treatment in the microbial reaction tank are supplied to the dilute active sludge aeration tank; and a step (6) in which treated raw water (2) separated from the dilute active sludge aeration tank is supplied to the settling tank.

Description

Activated sludge treatment method and repair method of existing wastewater treatment equipment using the method

The present invention relates to an activated sludge treatment method and a method for repairing an existing wastewater treatment facility using the activated sludge treatment method.

Since the activated sludge treatment method is an extremely excellent wastewater treatment method, it is widely used for wastewater treatment, and various treatment methods have been proposed depending on the type of raw water.
In the conventional activated sludge treatment method, various microorganisms are used from soil bacteria to large protozoa using a food chain.
An example of an existing activated sludge treatment method is shown in FIG.
The wastewater is introduced into the raw water adjustment tank, pretreated as necessary, and the one that has been dispersed in the raw water from the rough to the fine in the pressurized flotation tank is removed. In the case of drainage containing a large amount of oil, separation and flocculation with a flocculant is performed as a primary treatment. For example, an inorganic flocculant such as aluminum sulfate called a sulfate band or polyaluminum chloride called a pack, or an organic flocculant such as a polyacrylamide polymer is added to the effluent to break the emulsion state. The oil component and the water component are separated. However, in this case, the flocculant is generated in a large amount as sludge. Further, during the treatment in the pressurized levitation tank, the pollutant contained in the raw water is attached to and removed from the inorganic flocculant and becomes floating scum and is generated as sludge. These sludges are collected in a sludge storage tank.
The soluble organic component suitable for microbial treatment is sent to the aeration tank as treated raw water and aerated with activated sludge. The treated raw water is separated from the activated sludge and discharged, and the concentrated activated sludge is collected in the sludge storage tank. Some of them are recycled in the aeration tank as return sludge.
The sludge collected in the sludge storage tank is sent to a dehydrator to become a dehydrated cake, which is landfilled, fungus fertilizer or incinerated.

Such an activated sludge treatment method has a problem to be solved as described below.
(1) In the case of raw water containing a large amount of hardly decomposable substances such as proteins, modified proteins, cellulose, starch and fats and oils, a large amount of dehydrated cake that generates malodor is generated as excess sludge. In order to reduce excess sludge, a method was proposed in which the aeration tank was enlarged and aerated for a long time to digest (lagoon method, oxidation ditch). However, this method has problems such as a lack of a site and a huge construction cost because a large amount of aeration tank is required when the amount of drainage is large and the load is large. Once bulking or processing abnormalities occur, it takes a lot of money and days to recover, and there is a problem in the stable operation of the factory.
(2) In carrying out the microbial treatment, it is necessary to neutralize the pH of the inflow raw water. However, the addition of a chemical for neutralization has a problem of not only costing the chemical but also promoting the corrosion of the equipment. In addition, there is a problem that the pH of the discharged treated water changes significantly when the hydrogen ion concentration (hereinafter referred to as pH) of the inflow raw water is adjusted.
(3) In the activated sludge method, when a harmful substance that sterilizes activated sludge flows, the activated sludge is damaged and easily loses the purification function of raw water or causes filamentous bacterial bulking. However, removal of these harmful substances is a problem because small amounts of sterilizing agents and substances that adversely affect activated sludge are not allowed to flow into the waste water.
(4) An activated sludge treatment plant that is treating a large amount of organic pollutants has the following problems. Inflow water is extremely reduced at night and on holidays. In addition, when the number of consecutive holidays increases, a certain amount of pollutant is not given and good activated sludge bacteria are reduced by over-aeration. Furthermore, sludge is demolished by overload. As a result, since stable growth of activated sludge bacteria cannot be ensured, activated sludge treatment capacity tends to be reduced due to the occurrence of bulking or sludge floating. In particular, bulking is likely to occur when there are large fluctuations in the pollutant components of the inflowing raw water or when a sudden load is applied after the holidays. In order to prevent this, a large raw water adjustment tank is built, and a large amount of raw water is stored to homogenize the raw water or to supply a constant amount of water to the aeration tank. However, there is a problem of site area limitation and construction cost.
(5) The high-speed aeration activated sludge treatment method is a wastewater treatment method with a small installation area and high efficiency, but because it is a complete mixing type where activated sludge and raw water always coexist, bulking due to filamentous bacteria is likely to occur. There's a problem. In general, sewerage treatment facilities are classified as intermediate treatment facilities, and have disappeared in recent years as facilities that cannot perform sufficient treatment.

In order to solve the above problems, the present applicant has developed a microbial reaction tank and a wastewater treatment method (Patent Document 1), and has made achievements in wastewater treatment in many fields.
Moreover, as one of the methods for reducing excess sludge, a method is disclosed in which the excess sludge is subjected to ozone treatment and then returned to the aeration tank (Non-Patent Document 1). In addition, there is known a method of returning to an aeration tank after treating with thermophilic bacteria, mechanically crushing, or chemically treating.
However, as diversification of wastewater treatment proceeds and regulations on environmental loads become stricter, it may be difficult to reduce excess sludge even in wastewater treatment by the above methods.
In addition, the existing wastewater treatment facility of the conventional method has a problem that a large amount of excess sludge is generated because the site area of the wastewater treatment facility is large and the activated sludge treatment is not sufficient.

Japanese Patent No. 4142138

The present invention has been made to address the above problems, and in the wastewater treatment method using the activated sludge treatment method, the activated sludge treatment method that substantially eliminates the generation of excess sludge and the existing sludge treatment method using the activated sludge treatment method. The purpose is to provide a method for repairing wastewater treatment facilities.

The activated sludge treatment method of the present invention comprises a raw water aeration adjustment tank, a pressurized flotation concentration separation tank, a diluted activated sludge aeration tank, a microbial reaction tank, and a sedimentation tank, and drainage is performed by a circulation system in which sludge circulates between the tanks. An activated sludge treatment method for treating,
Supplying the sludge 2 generated from the settling tank to the raw water aeration control tank to which raw water before treatment is supplied;
The raw water mixed with the sludge 2 is aerated in the raw water aeration adjusting tank so that the oxidation-reduction potential (hereinafter referred to as ORP) becomes a positive value, and then the adjusted raw water is separated by concentration under pressure. Supplying step 2 to the tank;
Supplying the sludge 1 generated by the treatment in the pressurized flotation concentration separation tank to the microorganism reaction tank;
Supplying the treated raw water 1 separated from the pressurized flotation concentration separation tank to the diluted activated sludge aeration tank;
Supplying the sludge 3 generated by processing in the microbial reaction tank and the discharged water to the diluted activated sludge aeration tank; and
And a step 6 of supplying the treated raw water 2 separated from the diluted activated sludge aeration tank to the settling tank.

The sludge 2 supplied to the raw water aeration adjusting tank is characterized in that the sludge concentration in the raw water aeration adjusting tank is supplied in the range of 500 to 8000 mg / L as activated sludge suspended solids (hereinafter referred to as MLSS). To do.
In addition, the microorganism reaction tank used in the activated sludge treatment method of the present invention is provided in an outer tank, a cylindrical inner tank disposed inside the outer tank and having openings on the upper and lower sides, and an upper part of the cylindrical inner tank. A circulation rate control device for controlling the circulation rate of the water to be treated, a cylindrical control plate provided on the upper outer periphery of the cylindrical inner tank for settling sludge, and the outer and inner sides of the cylindrical inner tank And a raw water supply port provided in the circulation path of the water to be treated circulating in the outer tank and the inner tank and a treated water discharge port provided in the upper part of the outer tank. ing.
The cylindrical inner tank constituting the microbial reaction tank is divided into a cylindrical upper part and a cylindrical lower part by a partition wall having a communication hole in the center part, and the cylindrical upper part has a truncated cone shape with an upper surface and a bottom surface opened at the top part. And an aerobic microorganism treatment tank provided with a plurality of air blowing holes around the communication hole in the upper part of the cylinder and at the periphery of the partition wall, and the lower part of the cylinder is an anaerobic microorganism treatment tank having an opening on the bottom surface. A stirring device is provided for stirring the inside of the microorganism treatment tank and the inside of the anaerobic microorganism treatment tank.
The microbial reaction tank has at least one measurement value selected from the pH of the water to be treated, the redox potential (hereinafter referred to as ORP), and the amount of dissolved oxygen (hereinafter referred to as DO) measured by the water quality measuring apparatus. Means for detecting and opening and closing of the liquid level control valve, vertical movement of the liquid level control plate, and air blown from the air blowing port provided in the circulation rate control device according to the detected measurement value Means for controlling the in-tank circulation rate of the water to be treated to 3 to 20 by controlling at least one quantity selected from the quantity. Here, the to-be-processed water circulation rate in a reaction tank means the quantity defined by following Formula.

Rate of treated water circulation = amount of treated water discharged from the upper part of the inner tank (m ³ / day) / raw water supply (m ³ / day)

The microorganism reaction tank is a tank in which the raw water supplied from the raw water supply port passes through the activated sludge settled together with the activated sludge inside the cylindrical inner tank, the outer peripheral surface of the cylindrical inner tank, and the lower part of the outer tank. It is characterized in that anaerobic microbial treatment and aerobic microbial treatment are continuously performed by circulating inside.
In particular, the raw water supply port is a plurality of discharge ports or slits provided in an annular raw water supply unit disposed below the opening of the anaerobic microorganism treatment tank. In addition, the lower cylindrical portion has a volume that is 1/10 to 1 times the volume of the upper cylindrical portion.

The repair method of the existing wastewater treatment facility of the present invention is a repair method for reducing the sludge generated in the wastewater treatment facility from the sludge generated in the existing wastewater treatment facility,
The refurbishing method includes a step of newly installing the microbial reaction tank in an existing or refurbished pressurized flotation concentration separation tank and a diluted activated sludge aeration tank, and the activated sludge of the present invention through the newly installed microbial reaction tank. And a circulation step of circulating the sludge by a treatment method.

The method of the present invention circulates sludge generated in a pressurized flotation concentration separation tank, activated sludge aeration tank and microbial reaction tank, which are used as wastewater treatment equipment, between each other by the method of claim 1 and By supplying a part of the sludge generated in the sludge aeration tank to the raw water aeration adjustment tank of the wastewater to be activated sludge treated, an activated sludge treatment method that does not substantially discharge excess sludge is obtained.
In addition, by installing the microbial reaction tank according to claim 3, the existing wastewater treatment facility to be refurbished can perform wastewater treatment that does not substantially discharge excess sludge.

It is a block diagram of the activated sludge processing method. It is sectional drawing of a microbial reaction tank. It is a figure which shows the to-be-processed water and the circulation path | route of activated sludge in a microbial reaction tank. It is a block diagram of the existing activated sludge processing method.

A block diagram of the activated sludge treatment method of the present invention is shown in FIG.
Sludge 1, sludge 2 and sludge 3 generated in the pressurized flotation concentration separation tank, diluted activated sludge aeration tank, microbial reaction tank and sedimentation tank, respectively, circulate through the routes shown in Step 1 to Step 5, respectively. The sludge is digested in the circulating process, and the surplus sludge amount is not substantially discharged. Hereinafter, each process is demonstrated in order.

Step 1:
Step 1 is a step of supplying the sludge 2 generated by the settling tank to the raw water aeration control tank of the wastewater to be treated with activated sludge.
The raw water aeration tank can be obtained by adding air blowing equipment to the existing raw water tank when renovating the existing wastewater treatment equipment.
A large solid content in the wastewater to be treated is removed with a screen or the like and stored in the raw water aeration control tank as the raw water to be treated. The sludge 2 generated in the sedimentation tank is supplied to this raw water aeration control tank and mixed with the raw water, which is likely to cause abnormal treatment of activated sludge such as refractory substances in raw water and harmful substances that destroy activated sludge. The pollutant is adsorbed on the sludge 2. The sludge 2 is sludge that has been treated in a diluted activated sludge aeration tank and passed through a sedimentation tank, and is therefore an activated sludge suitable for wastewater to be treated. For this reason, supplying sludge 2 to raw water prevents damage to activated sludge in a diluted activated sludge aeration tank and keeps activated sludge in a high state. The occurrence of the phenomenon is reduced, and the processing can be stabilized.

The sludge 2 supplied to the raw water aeration adjustment tank is supplied in a range where the sludge concentration in the raw water aeration adjustment tank is 500 to 8000 mg / L as MLSS. Preferably, it is supplied in a range of 1000 to 5000 mg / L. When the MLSS is less than 500 mg / L, the sludge 2 cannot adsorb the pollutant that adversely affects the activated sludge, so that the activated sludge treatment becomes unstable. Moreover, when MLSS exceeds 8000 mg / L, the sludge 2 will adsorb most of pollutants, and the biochemical oxygen demand (henceforth BOD) contained in process raw | natural water will reduce.

Step 2:
Step 2 is a step of supplying the raw water to the pressurized flotation concentration separation tank after adjusting the aeration of the raw water mixed with the sludge 2 in the raw water aeration adjustment tank so that the ORP of the raw water becomes a positive value. . By adjusting the aeration so as to have a positive value, activated sludge treatment can be performed in which hydrogen sulfide, ammonia, mercaptan, etc., which cause bad odor, are oxidized and odor is hardly emitted.
The aeration process in the raw water aeration control tank is performed by an aeration process in which the residence time of the raw water is 3 hours or longer, preferably 5 hours or longer. Aeration treatment is performed in the presence of sludge 2, and raw water containing sludge is supplied to a pressurized flotation concentration separation tank.

Step 3:
Step 3 is a step of supplying sludge 1 generated by processing in the pressurized flotation concentration separation tank to the microorganism reaction tank. Here, the sludge 1 is not dry sludge but sludge water containing water.
The raw water supplied to the pressurized flotation concentration separation tank is subjected to aeration treatment in the raw water aeration adjustment tank, and the pH is naturally adjusted by the pH buffering action of microorganisms. The chemicals and equipment necessary for neutralization are unnecessary. Therefore, not only can the site be used effectively, but also it can be processed without chemical injection, so the cost of chemicals can be saved.
In addition, even if there are harmful substances such as disinfectants that adsorb to the activated sludge and destroy the activated sludge in the raw water, the sludge 2 adsorbs these in advance and is removed as pressurized sludge 1 outside the system. Since the activated sludge in the diluted activated sludge aeration tank is not adversely affected, stable activated sludge treatment can be performed even when the disinfectant is mixed into the waste water.

Step 4:
Step 4 is a step of supplying the treated raw water 1 separated from the pressurized flotation concentration separation tank to the diluted activated sludge aeration tank for treatment.
As the lean activated sludge aeration tank, the aerobic activated sludge treatment tank used in the existing activated sludge treatment method can be used as it is.
The raw activated water 1 is supplied to the diluted activated sludge aeration tank, and the sludge 3 generated in the microbial reaction tank shown in step 5 is supplied. The sludge 3 is digested by aeration with an oxygen-containing gas for 1 to 7 days in a lean activated sludge aeration tank to form digested sludge.

Step 5:
Step 5 is a step of supplying the sludge 3 generated by processing in the microorganism reaction tank to the diluted activated sludge aeration tank.
In the present invention, anaerobic treatment refers to treatment in a state where DO is less than 0.05 mg / L, and aerobic treatment refers to DO of 0.05 mg / L or more, preferably 0.1 mg / L or more, more preferably The treatment in a state of 0.2 mg / L or more. Further, the anaerobic treatment is an operation in which ORP is less than −80 mV, and in the aerobic treatment, ORP is −80 mV or more, preferably in a positive state.
In the microbial reaction tank, the sludge 1 is subjected to anaerobic / aerobic digestion, and most of the pollutants adsorbed by the sludge 1 are decomposed into gases such as carbon dioxide, water, nitrogen gas, and methane gas. Moreover, since the sludge 1 is used for the growth of microorganisms, and most of it becomes digested sludge that has been transformed into cells, the amount of sludge is significantly reduced. Even if a very small amount of sludge is generated, the sludge has good agglomeration and dewatering properties, and the water content of the dewatered cake is reduced, so that the amount of dewatered cake generated is significantly reduced.
Since the obtained dehydrated cake is a dehydrated cake of sludge 3 obtained in the state of fully mature cells, the moisture content is low, the generation of malodor can be suppressed, and the dehydrated cake can be disposed of in landfill at a low sludge treatment cost.

The microbial reaction tank can be composed of two tanks: a thick sludge anaerobic microbial reaction tank and an aerobic microbial reaction tank having a larger internal volume than the anaerobic microbial reaction tank.
Here, the anaerobic microorganism reaction tank should just be a tank which can process activated sludge on anaerobic conditions. The aerobic microorganism reaction tank is an activated sludge reaction tank substantially the same as the activated sludge aeration tank. Note that a gas containing oxygen may be supplied as necessary.
The amount of sludge 3 generated in the aerobic microorganism reaction tank is supplied to the diluted activated sludge aeration tank. The amount of dry sludge solids contained in the sludge 3 is approximately the same as the dry solid content of the reaction sludge contained in the diluted activated sludge aeration tank. The amount obtained by converting the concentration is supplied so that the amount of sludge in the diluted activated sludge aeration tank is kept constant. For example, when the reaction sludge having a concentration of 6000 mg / L contained in the diluted activated sludge aeration tank is supplied at 1 m ³ / hour, the sludge 3 having a concentration of 22000 mg / L may be supplied at 0.27 m ³ / hour. . However, when the amount of water entering the lean activated sludge aeration tank decreases, the amount of sludge 3 supplied is set to 20 to 200% of the normal amount.

A microbial reactor is shown in FIG. FIG. 2 is a cross-sectional view of the microbial reaction tank.
The microbial reaction tank 1 includes an outer tank 2, a cylindrical inner tank 3 disposed in the outer tank 2, a circulation rate control device 4 provided on the upper part of the cylindrical inner tank 3, and a cylindrical shape The cylindrical control board 5 provided in the outer peripheral side of the inner tank 3, the to-be-processed water quality measuring apparatus 6, and the sludge extraction port 13 are comprised.

The outer tub 2 has a true cylindrical appearance including a cylindrical side surface 2b and an upper surface portion 2c on a base 2a serving as a bottom surface. A rotating shaft 7 for attaching a stirring blade or the like is provided at the center of the cylinder. The rotary shaft 7 is rotatably fixed by a frame 2d provided at the center of the circle of the base 2a and a bearing 2e provided at the center of the circle of the upper surface portion 2c. The rotating shaft 7 is rotated by the driving device 2f. The upper surface portion 2c fixes the rotating shaft 7 rotatably, and holds the cylindrical inner tank 3 with a support or the like.
A raw water supply port 10 is provided at the bottom of the outer tub 2. The raw water supply port 10 includes a plurality of discharge ports 10b or slits provided in the annular raw water supply unit 10a, which are disposed below the lower opening 3f of the cylindrical inner tank 3. By disposing the raw water supply port 10 in this way, the anaerobic sludge is sufficiently stirred. The raw water supply port 10 can be provided in addition to the lower part of the cylindrical inner tank 3 as long as it is a circulation path of the water to be treated.
In addition, a purified treated water discharge port 11 is provided at the upper part of the outer tub 2, and a settling immobilization prevention device 12 for preventing sedimentation and fixation of settled sludge is provided on the inner surface of the outer tub. Yes.

As the settling and fixing prevention device, (1) a vibration device provided on the inner wall or the outer wall of the lower part of the outer tank where sludge settles, (2) a vibration plate provided near the inner wall, and an upper part of the outer tank. An apparatus having a vibration generator for transmitting vibration to the diaphragm, (3) a scraper provided on the inner wall of the lower part of the outer tank where the sludge settles, and (4) generating a stirring flow of sludge along the inner wall of the lower part of the outer tank. It is a stirring flow generating device, in particular a movable fluid spray nozzle that sprays fluid while moving on the inclined surface of the inner wall, or a fluid spray nozzle fixed to the inclined surface of the inner wall at a predetermined interval, (5) The stirring flow generator is a pump that draws sludge settled in the lower part of the outer tank while moving to the inclined surface or lower surface of the inner wall and discharges it into the anaerobic microorganism treatment tank, or a predetermined interval on the inclined surface or lower surface of the inner wall Fixed in Include a pump for discharging by suction the sludge settled at the bottom outer tank anaerobic microbial treatment vessel.

The cylindrical inner tub 3 is disposed in the outer tub provided with the settling and fixing prevention device 12.
The cylindrical inner tank 3 having a substantially circular cross section is divided into a cylindrical upper part 3c and a cylindrical lower part 3d by a partition wall 3a. A communication hole 3b is provided in the central portion of the partition wall 3a to connect the cylindrical upper part 3c and the cylindrical lower part 3d.
Even when the volume of the microorganism reaction tank is increased due to the presence of the partition wall 3a, the cylindrical upper part 3c and the cylindrical lower part 3d are sufficiently separated, and activated sludge treatment can be performed in each tank. The aerobic microorganism treatment reaction can be sufficiently performed in the cylindrical upper portion 3c, and the anaerobic microorganism treatment reaction can be sufficiently performed in the cylindrical lower portion 3d. When the area of the partition wall 3a becomes large, it is reinforced with a support member 3g or the like.
The communication hole 3b has a diameter that allows the activated sludge treated with anaerobic microorganisms to move from the cylindrical lower part 3d to the cylindrical upper part 3c, which is an aerobic microorganism treatment tank. The diameter of the communication hole 3b is adjusted by the volume of the microorganism reaction tank, the nature and amount of raw water to be treated, and the like.

The cylindrical upper portion 3c has a truncated cone-shaped top portion whose upper surface and bottom surface are open. That is, it is a shape in which the tip of the cylindrical portion is reduced in diameter by a predetermined angle in the height direction. The inclination angle of the cross section in the height direction passing through the center of the truncated cone is 40 to 60 degrees, preferably 45 degrees. By making the inclination angle within this range, the sludge contained in the water to be treated discharged from the upper part of the aerobic tank is likely to aggregate by flowing down the frustoconical outer surface, and the sludge can be rapidly forced to settle. Moreover, when sludge aggregates, separation of the sludge and the purified treated water becomes easy.
The cylindrical upper portion 3c is an aerobic microorganism treatment tank in which

air blowing ports

8 and 8a are provided. The air blowing port 8 is provided around the central shaft 7 and around the communication hole 3b, and can be fixed on the partition wall 3a by a support pillar (not shown). It is preferable that the air outlet of the air inlet 8 is preferably disposed downward because it can contribute to the agitation of the water to be treated and sludge in the aerobic tank.
The air blowing port 8a has a plurality of air holes 8c or air blowing portions 8b provided in the air blowing portion 8b. It can be made into the slit formed in the upper surface or side surface of this.
The amount of water to be treated is varied within the range of 3 to 20 without using a circulation pump, depending on the amount of air blown from the

air blowing ports

8 and 8a and the control amount of the circulation rate control device described later. Can do. Thereby, the aerobic microorganism treatment by an appropriate nitrification condition and the anaerobic microorganism treatment by an appropriate denitrification condition can be easily set. Furthermore, because the sludge solid-liquid separation is made very efficient by the forced sedimentation principle on the outer peripheral surface of the aerobic microorganism treatment tank having the above-mentioned inclination angle, the aerobic / anaerobic microorganism treatment reaction is efficiently carried out in the same vertical tank. Can be done.
In the aerobic tank, an alkali supply port or an acid supply port (not shown) can be provided.

The cylindrical lower part 3d is an anaerobic microorganism treatment tank having a volume that is 1/10 to 1 times the volume of the upper part of the cylinder. Within this volume range, for example, an aerobic microbial treatment reaction and an anaerobic microbial treatment reaction of raw water containing a high-concentration nitrogen-containing pollutant can be efficiently performed. In the anaerobic microorganism treatment tank, a denitrifying nutrient supply port (not shown) can be provided.
In addition, when there are few hydrogen donors in the raw water and nitrogen is denitrified by supplying a nitrogen donor such as methanol or acetic acid, the volume of the anaerobic microorganism treatment tank is made larger than that of the aerobic microorganism treatment tank. It is preferable.
The shape of the cylindrical lower portion 3d is a shape having an inverted truncated cone shape having an opening 3f having a larger area than the opening 3e of the cylindrical upper portion 3c at the lower portion of the cylinder. That is, it is a shape in which the tip of the cylindrical portion is reduced in diameter by a predetermined angle in the lower direction. By increasing the area of the opening 3f, the sludge can be easily stirred in the anaerobic microorganism treatment tank.
When the shape of the cylindrical lower portion 3d is the inverted truncated cone shape, it is preferable that the lower inner surface 2g of the outer tub 2 has the same angle as the predetermined angle because it is possible to prevent sludge from being settled and fixed.

The cylindrical inner tank 3 is provided with a stirring device for sufficiently carrying out the treatment reaction between the water to be treated and the activated sludge in the aerobic microorganism treatment tank as the cylinder upper part 3c and in the anaerobic microorganism treatment tank as the cylinder lower part 3d. Is provided.
The stirring device is preferably stirring

blades

7 a and 7 b fixed to a rotating shaft 7 attached to the center of the cylindrical inner tank 3. The stirring blade 7a is preferably provided in the cylindrical upper part 3c, and a turbine blade capable of sufficiently performing the aerobic microorganism treatment reaction is preferable. In addition to the turbine blade, any shape can be used as long as the number of rotations at which the aeration performance is not significantly lowered by the amount of air blown is relatively small and the air and water can be mixed.
The stirring blade 7b is a propeller blade that is provided in the cylindrical lower portion 3d and can sufficiently perform the anaerobic microorganism treatment reaction.

A partition wall 3 a provided in the cylindrical inner tub 3 is supported by a support column 9 that is fixed and erected on a base 2 a that is a bottom surface of the outer tub 2.
The cylindrical inner tank 3 is held in the outer tank by a support by the support column 9 and a support tool bridged to the upper part of the outer tank 2.

A circulation rate control device 4 for controlling the circulation rate in the reaction tank of the water to be treated is provided on the upper part of the cylindrical inner tank 3. Specifically, the control of the circulation rate of the water to be treated in the reaction tank by the circulation rate control device 4 is performed by opening and closing the liquid level control valve or vertically moving the liquid level control plate. When the liquid level control valve is fully opened or at the lowest level of the liquid level control plate, the water level of the water to be treated becomes the lowest. The water level is indicated by A.
Control of the circulation rate in the reaction tank can also be controlled by the amount of air blown from the air blowing port 8 and / or 8a. Increasing the amount of air blown increases the circulation rate. It is also possible to combine the opening and closing of the liquid level control valve and the air amount control.
As the anaerobic microorganism treatment tank and aerobic microorganism treatment tank increase in size, maintaining the circulating flow rate of sludge is not sufficient with aeration air alone, or harmful effects due to excessive air blowing may occur. There is. In preparation for such a case, the air inlet shown by 8a of FIG. 2 is needed. Due to the air blowing port 8a having poor aeration efficiency, there is an advantage that the adjustment of the air blowing amount and the ORP is much easier to adjust. For example, the air blowing port 8a is provided with an air blowing portion 8b having an annular shape in plan view, which is in communication with an external blower or the like around the stirring blade 7a in an aerobic portion which is the upper surface of the partition wall 3a. The part 8b is provided with a hole or a slit. This not only simply increases the amount of air, but also exhibits a baffle effect of the stirring blade 7a, and exhibits a synergistic effect that allows efficient stirring.

By adjusting the opening and closing of the liquid level control valve and / or the air blowing amount, the circulation rate of the water to be treated can be changed without using a pump. As will be described later, the water to be treated is treated from the aerobic microorganism treatment tank 3c to the anaerobic microorganism treatment tank 3d through the cylindrical control plate 5 disposed outside the tank, and further from the anaerobic microorganism treatment tank 3d. By circulating to the tank 3c, denitrification, dephosphorization, etc. are performed. Therefore, optimal denitrification, dephosphorization, etc. can be performed by controlling the circulation rate of the water to be treated based on a predetermined control program according to the detected value.

A cylindrical control plate 5 is disposed on the upper outer periphery of the cylindrical inner tank 3. The cylindrical control plate 5 is a cylinder whose upper and lower surfaces are open, and the lower surface 5 a of the cylindrical control plate 5 is disposed close to the inclined surface of the cylindrical inner tank 3. A sludge sedimentation portion is formed in the inclined surface portion disposed close to the slurry, and sludge is concentrated and treated water is separated. Moreover, the rapid forced sedimentation of sludge is attained by arrange | positioning the lower surface 5a close. The distance between the lower surface 5a and the inclined surface of the cylindrical inner tub 3 is preferably adjustable. Moreover, the shape of the cylindrical control plate 5 can be a right cylindrical shape in which the opening surfaces of the upper surface and the lower surface have the same area, or an inverted truncated cone shape in which the opening area of the upper surface is larger than the opening area of the lower surface.
In the microorganism reaction tank, a water quality measuring device 6 to be treated is provided inside and outside the cylindrical inner tank 2. This to-be-processed water quality measuring apparatus 6 is an apparatus which measures pH, ORP, and DO of to-be-processed water.

The circulation rate of water to be treated in the microorganism reaction tank is 3 to 20, preferably 5 to 20. If the circulation rate of the treated water is less than 3, the aerobic microbial treatment reaction is more likely to occur, and if it exceeds 20, the balance between the aerobic microbial treatment reaction and the anaerobic microbial treatment reaction is lost, and the denitrification and desorption of raw water Unable to perform phosphorus. That is, by setting the treated water circulation rate within this range, the ORP of the treated water measured by the treated water quality measuring device is −10 mV or less, preferably −50 mV or less, and the aerobic microorganism treatment in the anaerobic microorganism treatment reaction tank. In the reaction vessel, it can be maintained at +10 mV or more, preferably +100 mV or more. As a result, the aerobic microorganism treatment reaction and the anaerobic microorganism treatment reaction are sufficiently performed, and denitrification and dephosphorization are continuously performed. Under such conditions, the pH in the aerobic microorganism treatment reaction tank is in the range of 4.5 to 8.5, preferably 5.5 to 7.5.

The wastewater treatment method using the microbial reaction tank 1 has the following excellent characteristics as compared with the conventional wastewater treatment method.
In the conventional wastewater treatment method, raw water and return sludge are mixed in a certain ratio and flow into the aeration tank, and then the returned sludge in contact with the sludge and treated water are separated in the sedimentation tank, which is the next step. The raw water is pushed out and flows until it is done.
The waste water treatment method using the microbial reaction tank 1 is a method in which a circulating flow of activated sludge circulating up and down is formed, and raw water is added to the circulating flow. It is an energy-saving wastewater treatment method because the sludge circulation flow is formed by using the upflow by aeration air used for microbial treatment without using a circulation pump to make the circulation flow of activated sludge. Furthermore, it is the processing method which can implement aeration of an aerobic microorganism processing tank efficiently.
The raw water may be added anywhere in the circulation flow path, but is preferably an aerobic microorganism treatment tank. More preferably, an anaerobic microorganism treatment tank is suitable. In the case of treatment using a circulating flow in the wastewater treatment method of the present invention, even if the raw water has at least a BOD of 800 mg / L and a total nitrogen amount (hereinafter referred to as TN) of 40 mg / L or more, the treated water The BOD is usually extremely low, 20 mg / L or less, and generally the water quality of the discharged water can be operated at a BOD of 10 mg / L or less.
In addition, if raw water is added to the sludge sedimentation part in the circulation flow path formed on the outer peripheral surface of the cylindrical inner tank that is an aerobic microorganism treatment tank, the contact between the sludge and the raw water becomes insufficient, and Adsorption may be insufficient. In that case, contaminated substances in the raw water which is partially untreated may be mixed with the treated water, resulting in deterioration of the treated water. However, when the water quality regulation value is loose, raw water can be added to the sludge sedimentation part in the circulation flow path, for example, as a primary treatment facility such as sewage discharge with a BOD of 300 mg / L or less or 600 mg / L or less. There is a case.

Hereinafter, the circulation of water to be treated and activated sludge in the microorganism reaction tank 1 will be described with reference to FIG. FIG. 3 is a diagram showing a circulation path of water to be treated and activated sludge in the microorganism reaction tank 1. In FIG. 3, the hatched portion is a portion where the concentration of activated sludge is high, and the arrows indicate the circulation direction of the treated water and activated sludge.

The microorganism reaction tank 1 contains activated sludge in an amount of 5,000 to 12,000 mg / L in terms of solid content, and the treated raw water 1 first comes into contact with the activated sludge in an anaerobic state within the cylindrical lower part 3d to denitrify it. Reaction takes place. The treated raw water 1 supplied from the raw water supply port 10 and the circulated activated sludge are circulated in the lower part 3d of the cylinder by the rotation of the stirring blades or the air jet from the air diffuser to cause an anaerobic microorganism treatment reaction.
Next, the raw water and the activated sludge move through the communication hole 3b to the cylindrical upper portion 3c into which air is blown, and in contact with the activated sludge in the cylindrical upper portion 3c in an aerobic state, the rotation of the stirring blade or the air blowing port As a result of more air ejection, the nitrification reaction, which is an aerobic microorganism treatment reaction, proceeds in the cylindrical upper part 3c. As the nitrification reaction proceeds, the pH of the treated water decreases. The pH value, ORP, and DO of the liquid to be treated are measured by the treated water quality measuring device 6, and the circulation amount of the raw water or the water to be treated is determined based on these values. Specifically, the amount of air blown is adjusted so that the ORP can be maintained at +10 mV or more in an aerobic reaction treatment tank where nitrification reaction is performed, and -10 mV or less in an anaerobic reaction treatment tank where denitrification reaction is performed. Circulate treated water. The circulation amount can be easily achieved by controlling the air amount and / or the circulation rate control device without using a circulation pump or the like. For this reason, the wastewater treatment method of the present invention is an energy-saving wastewater treatment method. In addition, since the equipment including the microbial reaction tank of the present invention can adjust each unit of the microbial reaction, it is easy to program these controls in advance and automatically operate unattended. Have.

The circulation rate is controlled by the circulation rate control device 4, and the treated water and a part of the activated sludge discharged from the upper part of the cylindrical upper part 3c flow down on the frustoconical outer peripheral surface having an inclination angle of 45 degrees. The treated water and activated sludge that have flowed out pass through the cylindrical control plate 5 disposed close to the inclined surface of the frustoconical outer peripheral surface and the sludge concentrating portion 5b formed by the inclined surface. In addition, rapid forced sedimentation of activated sludge becomes possible. Moreover, separation of the purified treated water and activated sludge becomes easy, and the separated treated water is discharged from the treated water discharge port 11.
The activated sludge that has been rapidly forced to settle is concentrated and deposited between the inner surface of the outer tank and the outer peripheral surface of the inner tank. The accumulated activated sludge moves to the anaerobic microorganism treatment reaction section while mixing with the water to be treated and circulates in the microorganism reaction tank.
The wastewater treatment method of the present invention can easily absorb fluctuations in the load of raw water by circulating the inside of an anaerobic / aerobic tank at a circulation rate of 3 to 20 while the activated sludge is concentrated. Further, since the circulation rate is maintained within this range, the activated sludge is acclimatized and becomes an activated sludge that is optimal for wastewater treatment. Under such conditions, the pH in the aerobic treatment tank is in the range of 4.5 to 8.5, preferably 5.5 to 7.5.

In a microbial reaction tank, when the BOD load of raw water is small but the nitrogen concentration is high, denitrifying nutrients made of organic substances such as proton donors, such as methanol, are added to the anaerobic reaction treatment section. In this case, since the pH of the treated water is likely to increase, it is preferable to add a mineral acid such as hydrochloric acid.

The waste water treatment method of the present invention may use one microbial reaction tank or a plurality of tanks. In this case, the discharged water from the first tank is introduced into the raw water supply port of the second tank. For example, when two microbial reaction tanks are connected in series, the ratio of the volume of the nitrification reaction part and the volume of the denitrification reaction part in the second tank can be changed more effectively by changing the ratio in the first tank. Waste water treatment can be performed. Specifically, denitrification and dephosphorization can be performed by making the volume ratio smaller than that of the first tank.

By placing the microbial reaction tank in the wastewater treatment process, (1) the anaerobic and aerobic operation can be performed by suppressing the generation of harmful gases, so that the self-digestion ability of activated sludge cells is improved. As microbial cells capable of selectively degrading pollutants in raw water are acclimatized, it is possible to easily treat hardly decomposable substances.

Step 6:
Step 6 is a step of supplying the treated raw water 2 separated from the diluted activated sludge aeration tank to the settling tank. The sludge contained in the treated raw water 2 is precipitated in the settling tank, and the supernatant liquid is discharged as discharged water.

The renovation method of the existing wastewater treatment facility of the present invention is a method of newly adding the above microbial reaction tank to the existing wastewater treatment facility. By adding a new microbial reaction tank and circulating the sludge through this microbial reaction tank, the amount of sludge generated in the existing wastewater treatment equipment installed in the food manufacturing plant can be reduced to almost zero. . This eliminates the need for sludge storage tanks and dewatering devices that occupy an important part of existing wastewater treatment facilities, thereby reducing the installation area of the wastewater treatment facilities.

Example 1
The waste water discharged from the food manufacturing factory was treated by the method shown in FIG.
The wastewater before treatment has a BOD of 800 mg / L, a chemical oxygen demand (hereinafter referred to as COD) of 300 mg / L, TN of 50 mg / L, and a normal hexane extract oil concentration (hereinafter referred to as n-Hex). 50 mg / L, suspended solids concentration (hereinafter referred to as SS) is 200 mg / L, and the amount of treated water is 1500 m ³ / day. In addition, this waste water was conventionally drained by the method shown in FIG. 4, and dehydrated cake was generated at 150 tons / month.
The volume of the raw water aeration control tank is 1500 m ³ , the volume of the pressurized flotation concentration separation tank is 250 m ³ , the volume of the diluted activated sludge aeration tank is 1500 m ³ , and the volume of the sedimentation tank is 800 m ³ .
The microbial reaction tank has an anaerobic treatment tank with a volume of 80 m ^{3 and} an aerobic treatment tank with a volume of 250 m ³ . The treatment raw water circulation rate in the microbial reactor was circulated in the range of 3-6.

Sludge generated in the sedimentation tank was continuously added to the raw water aeration control tank using a metering pump. The addition amount was supplied in the range where the sludge concentration in the raw water aeration control tank was 1500 to 2000 mg / L as MLSS. Moreover, the amount of aeration was adjusted, and ORP was adjusted until it became + 50mV.
In the raw water aeration adjusting tank, the treated raw water that has been subjected to aeration adjustment so that the ORP has a positive value is supplied to a non-chemical casting pressurized flotation concentration separation tank KF800 (manufactured by Nippon Alcy Co., Ltd.). This pressurized flotation concentration separation tank mixes and circulates 100 parts by weight of 5 kg / cm ² of pressurized water without chemical injection with respect to 100 parts by weight of the treated raw water.

The sludge separated in the pressurized flotation concentration separation tank was sent to the microorganism reaction tank for processing. In the microorganism reaction tank, the pH in the anaerobic tank is 7.1, the ORP is -350 mV, the DO is 0, the pH in the aerobic tank is 6.1, the ORP is +210 mV, and the DO is 0.8 mg / L. there were.
Excess sludge generated in the microbial reaction tank was supplied to a diluted activated sludge aeration tank. The total amount of water discharged from the microbial reaction tank was supplied to the diluted activated sludge aeration tank.

The treated raw water obtained in the pressurized flotation concentration separation tank was sent to a diluted activated sludge aeration tank for treatment. Excess sludge generated in the microorganism reaction tank was supplied to the diluted activated sludge aeration tank. Excess sludge is acclimatized to the activated sludge suitable for the treated raw water in the diluted activated sludge aeration tank.

The treated raw water treated in the diluted activated sludge aeration tank was discharged through the sedimentation tank. Moreover, the sludge settled in the settling tank was circulated again to the raw water aeration control tank. Through this sludge circulation process, the amount of sludge can be reduced.
The water quality of the discharged water was 8 mg / L for BOD, 10 mg / L for COD, 0 mg / L for TN, 0 mg / L for n-Hex, and 1 mg / L for SS.
Further, the generation of dehydrated cake was 0 to 20 tons / month.

The wastewater treatment by the above method improves the self-digestion efficiency of the bacterial cells because the anaerobic and aerobic operation can be performed while suppressing the generation of harmful gases in the microbial reaction tank. Further, through the circulation of sludge, the bacterial cells capable of selectively decomposing the sludge substance in the raw water are acclimatized and the hardly degradable pollutant substance can be easily treated. As a result, effects such as (1) the amount of dehydrated cake discharged can be significantly reduced, and (2) the odor in the vicinity of the pressurized flotation concentration separation tank is eliminated.

Example 2
Wastewater discharged from the pastry factory was processed.
The waste water before treatment is 6000 mg / L for BOD, 3500 mg / L for COD, 120 mg / L for TN, 3000 mg / L for n-Hex, 3500 mg / L for ss, and the amount of treated water is 120 m ³ / day. is there. In this factory, an inorganic flocculant such as polyaluminum chloride was added to the pressurized flotation tank to cause coagulation precipitation, and then a conventional waste water treatment was performed by the method shown in FIG. For this reason, dehydrated cake (water content 85% by weight) was generated at 150 tons / month.
The sludge storage tank and dehydrator shown in FIG. 4 are removed, and a microbial reaction having a 100 m ³ anaerobic treatment tank and a 250 m ³ aerobic treatment tank shown in FIG. 2 in a part of the removed site. A tank was constructed. The treatment raw water circulation rate in the microbial reactor was circulated in the range of 5-8.
Moreover, the aeration apparatus was attached to the conventional raw | natural water adjustment tank shown in FIG. 4, and it modified into the raw | natural water aeration adjustment tank. The conventional aeration tank was reused as a dilute activated sludge aeration tank, and the settling tank was reused as a settling tank, and the sludge circulation path shown in FIG. 1 was attached to each.
The volume of the raw water aeration tank in this factory is 100 m ³ , the volume of the pressurized flotation concentration separation tank is 10 m ³ , the volume of the diluted activated sludge aeration tank is 120 m ³ , and the volume of the sedimentation tank is 30 m ^3. It is.

Sludge generated in the sedimentation tank was continuously added to the raw water aeration control tank using a metering pump. The added amount was supplied in a range where the sludge concentration in the raw water aeration adjusting tank was 3500 to 5000 mg / L as MLSS. Moreover, the amount of aeration was adjusted to adjust the ORP to +100 mV.
In the raw water aeration adjusting tank, the treated raw water that has been subjected to aeration adjustment so that the ORP has a positive value is supplied to a non-chemical casting pressurized flotation concentration separation tank KF800 (manufactured by Nippon Alcy Co., Ltd.). In this pressurized flotation concentration separation tank, 220 parts by weight of 4.5 kg / cm ² of pressurized water is mixed and circulated without chemical injection with respect to 100 parts by weight of the treated raw water.

The sludge separated in the pressurized flotation concentration separation tank was sent to the microorganism reaction tank for processing. In the microorganism reaction tank, the pH in the anaerobic tank is 7.4, the ORP is −400 mV, the DO is 0, the pH in the aerobic tank is 7.8, the ORP is +210 mV, and the DO is 1.8 mg / L. there were.
Excess sludge and discharge water generated in the microbial reactor were supplied to the diluted activated sludge aeration tank.

The treated raw water obtained in the pressurized flotation concentration separation tank was sent to a diluted activated sludge aeration tank in the same manner as in Example 1 for treatment, and the treated water was discharged through a precipitation tank. Moreover, the sludge settled in the settling tank was circulated again to the raw water aeration control tank.
The water quality of the discharged water was 18 mg / L for BOD, 30 mg / L for COD, 1 mg / L for TN, 1 mg / L for n-Hex, and 30 mg / L for SS.
Further, the generation of dehydrated cake was 0 ton / month.
The wastewater treatment at the confectionery factory also showed effects such as (1) a significant reduction in the amount of dehydrated cake discharged and (2) the elimination of odors near the pressurized flotation concentration separation tank.

Since the method of the present invention does not substantially discharge excess sludge, it is an environmentally friendly wastewater treatment method with little environmental destruction, and since no equipment for dewatering cake treatment is required, a number of existing wastewater treatments will be required in the future. It can be used as a repair method for equipment. . Particularly in factories in urban areas, a large amount of bad odor is generated from the raw water adjustment tank, the pretreatment facility, and the dehydration facility, and therefore, a deodorization facility is usually required. However, when this treatment method is introduced, no bad odor is generated from the raw water adjustment tank for wastewater treatment to the treatment process from final treatment. For this reason, the present processing method is a processing method suitable for countermeasures against malodors in which the generation of malodor associated with the processing is suppressed, for example, a deodorizing facility may be unnecessary.

DESCRIPTION OF SYMBOLS 1 Microbial reaction tank 2 Outer tank 3 Cylindrical inner tank 4 Circulation rate control apparatus 5 Cylindrical control board 6 Water quality measuring apparatus 7 Rotating shaft 8 Air inlet 9 Support pillar 10 Raw water supply port 11 Treated water discharge port 12 Settling fixation Prevention device 13 Sludge outlet

Claims

An activated sludge treatment method comprising a raw water aeration adjustment tank, a pressurized flotation concentration separation tank, a diluted activated sludge aeration tank, a microbial reaction tank, and a sedimentation tank, and the wastewater is treated by a circulation system in which the sludge circulates between each tank. ,
Supplying the sludge 2 generated from the settling tank to the raw water aeration control tank to which raw water before treatment is supplied; and
The raw water mixed with the sludge 2 is aerated in the raw water aeration adjusting tank so that the redox potential becomes a positive value, and then the adjusted raw water is supplied to the pressurized flotation concentration separation tank 2,
Supplying the sludge 1 generated by processing in the pressurized flotation concentration separation tank to the microorganism reaction tank;
Supplying the treated raw water 1 separated from the pressurized flotation concentration separation tank to the diluted activated sludge aeration tank; and
Supplying the sludge 3 generated by processing in the microorganism reaction tank and the discharged water to the diluted activated sludge aeration tank; and
And a step 6 of supplying the treated raw water 2 separated from the diluted activated sludge aeration tank to the settling tank.
The sludge 2 supplied to the raw water aeration control tank is supplied in a range where the sludge concentration in the raw water aeration control tank is 500 to 8000 mg / L as activated sludge suspended solids. Activated sludge treatment method.
The microbial reaction tank includes an outer tank, a cylindrical inner tank disposed in the outer tank and having openings on the upper and lower sides, and a circulation rate of water to be treated provided in the upper part of the cylindrical inner tank. A circulation rate control device for controlling, a cylindrical control plate for settling sludge provided on the upper outer periphery of the cylindrical inner tub, and a water quality measuring device to be treated provided on the outer and inner sides of the cylindrical inner tub And a raw water supply port provided in a circulation path of water to be treated that circulates in the outer tank and the inner tank, and a treated water discharge port provided in an upper part of the outer tank,
The cylindrical inner tank is divided into a cylindrical upper part and a cylindrical lower part by a partition wall having a communication hole in a central part, and the cylindrical upper part has a top part of a truncated cone shape having an upper surface and a bottom surface opened, and the upper part of the cylinder In the aerobic microorganism treatment tank provided with a plurality of air blowing openings around the communication hole and the peripheral edge of the partition, the cylindrical lower part is an anaerobic microorganism treatment tank having an opening on the bottom surface,
A stirrer for stirring the aerobic microorganism treatment tank and the anaerobic microorganism treatment tank is provided,
Means for detecting at least one measurement value selected from the hydrogen ion concentration, redox potential, and dissolved oxygen content of the water to be treated measured by the water quality measuring device, and depending on the detected measurement value, By controlling at least one amount selected from the opening and closing of the liquid level adjustment valve, the vertical movement of the liquid level adjustment control plate, and the amount of air blown from the air blowing port provided in the circulation rate control device, Means for controlling the in-tank circulation rate of treated water to 3-20,
The raw water supplied from the raw water supply port circulates in the tank together with the activated sludge through the inside of the cylindrical inner tank, the outer peripheral surface of the cylindrical inner tank, and the activated sludge settled in the lower part of the outer tank. The activated sludge treatment method according to claim 1, wherein the anaerobic microorganism treatment and the aerobic microorganism treatment are continuously performed.
A method of repairing an existing wastewater treatment facility that reduces the amount of sludge generated in a wastewater treatment facility from the amount of sludge generated in the existing wastewater treatment facility,
The refurbishing method includes the step of newly installing the microorganism reaction tank according to claim 3 together with the existing or refurbished pressurized flotation concentration separation tank and the diluted activated sludge aeration tank;
A method for refurbishing existing wastewater treatment equipment, comprising a circulation step of circulating sludge by the method according to claim 1 through the newly installed microorganism reaction tank.